1. Field of Invention
This invention relates generally to a sealing system for the drive shaft of a marine propeller, the system including a bearing and a lip seal coaxial with the shaft mounted adjacent one end of the bearing, and more particularly, to a system of this type which prior to being installed on the shaft is provided with a protector having a sleeve that is telescoped into the lip seal and acts as liner therefor to prevent the seal from being damaged when in the course of installation, the inboard end of the shaft is inserted through the lip seal.
1. Status of Prior Art
Our above-identified copending application discloses a sealing system for the drive shaft of a marine propeller, the shaft extending through the hull of a boat and being coupled at its outboard end to the propeller. The inboard end of the shaft is coupled to the transmission of a marine engine for turning the propeller. The sealing system disclosed in our copending patent application includes a cylindrical bearing surrounding the rotary drive shaft and an elastomeric lip seal coaxial with the shaft mounted within the bearing adjacent one end thereof to prevent water from leaking through the bearing into the boat.
Formed within the cylindrical body of the bearing is an annular reservoir within which the seal is positioned. Sea water conducted along the shaft within the bearing is fed into the reservoir and discharged therefrom back to the sea. This circulating flow of water acts to lubricate and cool the lip seal and thereby maintain it in working order. In the absense of such lubrication, the heat generated by the friction between the shaft and the seal would in time render the seal ineffective.
When installing a sealing system of this type, the inboard end of the drive shaft must be made to pass through the bearing and the lip seal mounted therein. We have found that in many instances the lip seal will be damaged by this installation procedure, for the inboard end of the shaft is not perfectly smooth and free of sharp edges, and in passing through the elastomeric lip seal it may abrade, score and otherwise mutilate the lip seal. As a consequence the installed sealing system may leak and not be effective for its intended purpose.
The reason there are sharp edges on the inboard end of the typical drive shaft is that it has a key way indented therein to lock the shaft to a coupling for the transmission of the marine engine. And there are also indentations to receive set screws to lock the coupling to the shaft. Moreover, the blunt end of the shaft has a fairly sharp circular edge. These sharp metal edges on the inboard end of the shaft cut into the lip of the elastomeric lip seal when the shaft is pushed therethrough, and may mutilate the seal and render it ineffective.
But this is not the only problem encountered in the course of installing, for the blunt end of the drive shaft, when seeking to pass through the lip seal, may catch it and distort its shape, causing the 360 degree retainer spring located in the shoulder of the lip seal and holding it in place in the bearing to pop out. Should the retainer spring be bumped from its seat, the life of the seal will be substantially shortened. The installation of a sealing system is a blind procedure, for the installer cannot see into the bearing. The installer therefore will not know whether the retainer spring for the lip seal has been dislodged from its seat.
Similar problems are encountered when retrofitting a sealing system several times in the course of a vessel's life. Each time the sealing system is installed on the drive shaft, the shaft will then bear scar marks left by wrenches, hammers, coupling pullers and other tools employed in making the installation. These marks and scars contribute to the damage inflicted by sharp edges when the shaft is forced through the elastomeric lip seal. Further damage to the lip seal results from rust and pitting formed on the surface of the drive shaft in the course of prolonged operation in the environment of the vessel.